Head-mounted compound display including a high resolution inset

ABSTRACT

A head-mounted display (HMD) that includes a high resolution (HR) inset display and a peripheral display. The HR inset display is configured to display an inset region that includes a portion of an image at a first resolution that corresponds to a resolution of a fovea region of a human eye. The peripheral display displays a background region, the background region having a second resolution that is less than the first resolution, the second resolution corresponding to a resolution of a non-fovea region of the human eye. The HMD includes an optics block that combines the inset region and the background region to create composite content at retinal resolution, and direct the composite content to an exit pupil of the HMD corresponding to a location of an eye of a user of the HMD.

BACKGROUND

The present disclosure generally relates to electronic displays, andspecifically relates to a head-mounted compound display including a highresolution inset.

Conventional displays present images at a constant resolution. Incontrast, resolution varies across a retina of a human eye. Though theeye receives data from a field of about 200 degrees, the acuity overmost of that range is poor. In fact, the light must fall on the fovea toform high resolution images, and that limits the acute vision angle toabout 15 degrees. In head-mounted displays, at any given time, only asmall portion of the image light emitted from the display is actuallyimaged onto the fovea. The remaining image light that is imaged ontoretina is imaged at other areas that are not capable of perceiving thehigh resolution in the emitted image light. Accordingly, some of theresources (e.g., power, memory, processing time, etc.) that went intogenerating the high resolution image being viewed by the user is wastedas the user is not able to perceive the portion of the image lightimaged outside the fovea at its full resolution.

SUMMARY

A head-mounted display (HMD) generates composite content at retinalresolution. Retinal resolution is defined as a composite image withvariable resolution that matches a resolution of a retina of a humaneye. Composite content is composed of a background region and an insetregion that together form an image at retinal resolution. The backgroundregion is a portion of an image at a resolution of a non-fovea region ofa human eye. The inset region includes a high resolution (HR) portion ofthe image that is surrounded by a transitional portion of the image. TheHR inset portion of the image is at a resolution corresponding to afovea region of the human eye. The transitional portion is blended suchthat its resolution smoothly varies between the resolution of the HRinset portion and the resolution of the background region. In alternateembodiments, the HR inset portion of the image is at a resolution higherthan the background region, but less than the resolution correspondingto the fovea region of the human eye. The HMD includes a peripheraldisplay and a HR inset display. The peripheral display presents thebackground region at its resolution, and the HR inset display presentsthe inset region according to its varying resolution. The HMD combinesthe light from the two displays such that composite content is formed atretinal resolution.

The compound display assembly may be configured to generate compositecontent having a fixed inset region or a steered inset region. A fixedinset region is an inset region that is fixed in relation to thebackground region. A steered inset region is an inset region having aposition that may be varied in composite content. In a steered insetregion configuration, the compound display assembly also includes an eyetracking unit that tracks gaze direction of a viewing user and uses asteering element to adjust a position of the inset region in thegenerated composite content such that it is centered on the gazedirection. As the gaze direction changes, the compound display assemblysteers the inset region to keep it centered on the gaze direction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a system environment including a virtual realitysystem, in accordance with an embodiment.

FIG. 2A is a diagram of a virtual reality headset, in accordance with anembodiment.

FIG. 2B is a cross section of a front rigid body of the VR headset inFIG. 2A, in accordance with an embodiment.

FIG. 3 is a high-level block diagram illustrating a detailed view ofmodules within a compound display assembly, in accordance with anembodiment.

FIG. 4A are example non-pupil forming designs of a compound displayconfigured to generate composite content having a fixed inset region, inaccordance with an embodiment.

FIG. 4B are example pupil forming designs of a compound displayconfigured to generate composite content having a fixed inset region, inaccordance with an embodiment.

FIG. 5 illustrates the acuity for a human eye and various exampledisplays in accordance with an embodiment.

FIG. 6A is an example design of a compound display assembly configuredto generate composite content having a fixed inset region, in accordancewith an embodiment.

FIG. 6B is a perspective view of a compound display assembly configuredto generate composite content having a fixed inset region, in accordancewith an embodiment.

FIG. 6C is a top view of the compound display assembly shown in FIG. 6B,in accordance with an embodiment.

FIG. 7 is an example design of a compound display configured to generatea steered HR including a steered high resolution inset, in accordancewith some embodiments.

FIG. 8 is flowchart for generating an image at retinal resolution, inaccordance with some embodiments.

FIG. 9A illustrates a peripheral content of an image displayed via acompound display assembly, in accordance with some embodiments.

FIG. 9B illustrates a set of inset masks for changing a resolution of animage to display via a compound display assembly, in accordance withsome embodiments.

FIG. 9C illustrates composite content including variable resolutionsdisplayed via a compound display assembly, in accordance with someembodiments.

The figures depict embodiments of the present disclosure for purposes ofillustration only. One skilled in the art will readily recognize fromthe following description that alternative embodiments of the structuresand methods illustrated herein may be employed without departing fromthe principles of the disclosure described herein.

DETAILED DESCRIPTION

System Overview

FIG. 1 is a block diagram of a virtual reality (VR) system environment100 in which a VR console 110 operates. The system environment 100 shownby FIG. 1 comprises a VR headset 105, an imaging device 135, and a VRinput interface 140 that are each coupled to the VR console 110. WhileFIG. 1 shows an example VR system environment 100 including one VRheadset 105, one imaging device 135, and one VR input interface 140, inother embodiments any number of these components may be included in theVR system environment 100. For example, there may be multiple VRheadsets 105 each having an associated VR input interface 140 and beingmonitored by one or more imaging devices 135, with each VR headset 105,VR input interface 140, and imaging devices 135 communicating with theVR console 110. In alternative configurations, different and/oradditional components may be included in the VR system environment 100.Similarly, functionality of one or more of the components may bedistributed among the components in a different manner than is describedhere. For example, some or all of the functionality of the VR console110 may be contained within the VR headset 105.

The VR headset 105 is a head-mounted display that presents content to auser. Examples of content presented by the VR headset 105 include one ormore images, video, audio, or some combination thereof. In someembodiments, audio is presented via an external device (e.g., speakersand/or headphones) that receives audio information from the VR headset105, the VR console 110, or both, and presents audio data based on theaudio information. Some embodiments of the VR headset 105 are furtherdescribed below in conjunction with FIGS. 2A-2B, 3-6. The VR headset 105may comprise one or more rigid bodies, which may be rigidly ornon-rigidly coupled to each other. A rigid coupling between rigid bodiescauses the coupled rigid bodies to act as a single rigid entity. Incontrast, a non-rigid coupling between rigid bodies allows the rigidbodies to move relative to each other. In some embodiments, the VRheadset 105 may also act as an augmented reality (AR) headset. When theVR headset acts as an AR headset, the VR headset 105 augments views andof a physical, real-world environment with computer-generated elements(e.g., images, video, sound, etc.).

The VR headset 105 includes a compound display assembly 160, one or morelocators 120, one or more position sensors 125 and an inertialmeasurement unit (IMU) 130. Some embodiments of the VR headset 105 havedifferent components than those described here. Similarly, thefunctionality of various components may be distributed among othercomponents in the VR system environment 100 in a different manner thanis described here in various embodiments. For example, some of thefunctions of the compound display assembly 160 may be performed by theVR console 110.

The compound display assembly 160 displays an image that is at a retinalresolution. Retinal resolution is defined as a composite image withvariable resolution that matches or exceeds a resolution of a retina ofa human eye. The compound display assembly 160 combines two or moreimages at different resolutions to generate composite content at retinalresolution. Composite content includes an inset region and a backgroundregion. The inset region is a portion of the composite content that hasa resolution on the order of a fovea region of a retina of a human eye.The inset region includes a HR inset portion and a transitional portion.The HR inset portion is at a resolution corresponding to a fovea regionof a human eye. In alternate embodiments, the HR inset portion of theimage is at a resolution higher than the background region, but lessthan the resolution corresponding to the fovea region of the human eye.The transitional region surrounds the HR inset portion, and has avariable resolution that facilitates a seamless blending of the insetregion with the background region. The variable resolution is such thatit generally matches a transition found in the human eye between thefovea region and the non-fovea region of the retina. The backgroundregion of composite content surrounds some or all of the inset region,and is at a resolution generally on the order of a non-fovea region ofthe retina.

The compound display assembly 160 includes a HR inset display and aperipheral display. The HR inset display displays the inset region. TheHR inset display displays the HR inset portion of the inset region at aresolution higher than the peripheral display, and is on the order of ahuman eye's visual acuity within the fovea region of the retina. The HRinset display displays the transitional region with a smoothly varyingresolution. In contrast, the peripheral display displays the backgroundregion at a low resolution that is on the order of a human eye's visualacuity outside a fovea region of the retina. The compound displayassembly 160 includes various optics which combine the inset region andthe background region to generate composite content for presentation toa viewing user.

In some embodiments, the compound display assembly 160 receives an imageat a particular resolution. The resolution may be, e.g., at least theresolution of the inset region display. The image is divided into a HRinset portion, a transitional portion, and a peripheral portion. Thecompound display assembly 160 may adjust a resolution of the HR insetportion of the image for presentation via the HR inset display.Additionally, the compound display assembly 160 adjusts a resolution ofthe peripheral portion of the image for presentation via the peripheraldisplay. The compound display assembly 160 adjusts the resolution of thetransitional portion such that it blends the inset portion and theperipheral portion. This would allow the peripheral display to be auniform low resolution display with a resolution on the order of anon-fovea region of the retina. In contrast, in alternate embodimentssome of the transitional region is presented using the peripheraldisplay, accordingly, the peripheral display may have a variableresolution that transitions the inset portion of the image to theperipheral portion of the image.

In some embodiments, the compound display assembly 160 is configured togenerate composite content having a fixed inset region. A fixed insetregion is an inset region that is fixed in relation to the backgroundregion. A viewing user tends to look towards a center of displayedcontent. In some embodiments, the fixed inset region is fixed at thecenter of the background region.

In other embodiments, the compound display assembly 160 is configured togenerate composite content having a steered inset region. A steeredinset region is an inset region having a position that may be varied incomposite content. The compound display assembly 160 may include an eyetracking unit that tracks gaze direction of a viewing user, and may use,e.g., a steering mirror to adjust a position of an inset region in thegenerated composite content such that it is centered on the gazedirection. As the gaze direction changes, the compound display assembly160 steers the inset region to keep it centered on the gaze direction.Operation of the compound display assembly 160 is discussed in detailbelow with regard to FIGS. 2-9C.

The locators 120 are objects located in specific positions on the VRheadset 105 relative to one another and relative to a specific referencepoint on the VR headset 105. A locator 120 may be a light emitting diode(LED), a corner cube reflector, a reflective marker, a type of lightsource that contrasts with an environment in which the VR headset 105operates, or some combination thereof. In embodiments where the locators120 are active (i.e., an LED or other type of light emitting device),the locators 120 may emit light in the visible band (˜380 nm to 750 nm),in the infrared (IR) band (˜750 nm to 1700 nm), in the ultraviolet band(10 nm to 380 nm), in some other portion of the electromagneticspectrum, or in some combination thereof.

In some embodiments, the locators 120 are located beneath an outersurface of the VR headset 105, which is transparent to the wavelengthsof light emitted or reflected by the locators 120 or is thin enough notto substantially attenuate the wavelengths of light emitted or reflectedby the locators 120. Additionally, in some embodiments, the outersurface or other portions of the VR headset 105 are opaque in thevisible band of wavelengths of light. Thus, the locators 120 may emitlight in the IR band under an outer surface that is transparent in theIR band but opaque in the visible band.

The IMU 130 is an electronic device that generates fast calibration databased on measurement signals received from one or more of the positionsensors 125. A position sensor 125 generates one or more measurementsignals in response to motion of the VR headset 105. Examples ofposition sensors 125 include: one or more accelerometers, one or moregyroscopes, one or more magnetometers, another suitable type of sensorthat detects motion, a type of sensor used for error correction of theIMU 130, or some combination thereof. The position sensors 125 may belocated external to the IMU 130, internal to the IMU 130, or somecombination thereof.

Based on the one or more measurement signals from one or more positionsensors 125, the IMU 130 generates fast calibration data indicating anestimated position of the VR headset 105 relative to an initial positionof the VR headset 105. For example, the position sensors 125 includemultiple accelerometers to measure translational motion (forward/back,up/down, left/right) and multiple gyroscopes to measure rotationalmotion (e.g., pitch, yaw, roll). In some embodiments, the IMU 130rapidly samples the measurement signals and calculates the estimatedposition of the VR headset 105 from the sampled data. For example, theIMU 130 integrates the measurement signals received from theaccelerometers over time to estimate a velocity vector and integratesthe velocity vector over time to determine an estimated position of areference point on the VR headset 105. Alternatively, the IMU 130provides the sampled measurement signals to the VR console 110, whichdetermines the fast calibration data. The reference point is a pointthat may be used to describe the position of the VR headset 105. Whilethe reference point may generally be defined as a point in space, inpractice the reference point is often defined as a point within the VRheadset 105 (e.g., a center of the IMU 130).

The IMU 130 receives one or more calibration parameters from the VRconsole 110. As further discussed below, the one or more calibrationparameters are used to maintain tracking of the VR headset 105. Based ona received calibration parameter, the IMU 130 may adjust one or more IMUparameters (e.g., sample rate). In some embodiments, certain calibrationparameters cause the IMU 130 to update an initial position of thereference point so it corresponds to a next calibrated position of thereference point. Updating the initial position of the reference point asthe next calibrated position of the reference point helps reduceaccumulated error associated with the determined estimated position. Theaccumulated error, also referred to as drift error, causes the estimatedposition of the reference point to “drift” away from the actual positionof the reference point over time.

The imaging device 135 generates slow calibration data in accordancewith calibration parameters received from the VR console 110. Slowcalibration data includes one or more images showing observed positionsof the locators 120 that are detectable by the imaging device 135. Theimaging device 135 may include one or more cameras, one or more videocameras, any other device capable of capturing images including one ormore of the locators 120, or some combination thereof. Additionally, theimaging device 135 may include one or more filters (e.g., used toincrease signal to noise ratio). The imaging device 135 is configured todetect light emitted or reflected from locators 120 in a field of viewof the imaging device 135. In embodiments where the locators 120 includepassive elements (e.g., a retroreflector), the imaging device 135 mayinclude a light source that illuminates some or all of the locators 120,which retro-reflect the light towards the light source in the imagingdevice 135. Slow calibration data is communicated from the imagingdevice 135 to the VR console 110, and the imaging device 135 receivesone or more calibration parameters from the VR console 110 to adjust oneor more imaging parameters (e.g., focal length, focus, frame rate, ISO,sensor temperature, shutter speed, aperture, etc.).

The VR input interface 140 is a device that allows a user to send actionrequests to the VR console 110. An action request is a request toperform a particular action. For example, an action request may be tostart an application, to end an application, or to perform a particularaction within the application. The VR input interface 140 may includeone or more input devices. Example input devices include: a keyboard, amouse, a game controller, or any other suitable device for receivingaction requests and communicating the received action requests to the VRconsole 110. An action request received by the VR input interface 140 iscommunicated to the VR console 110, which performs an actioncorresponding to the action request. In some embodiments, the VR inputinterface 140 provides haptic feedback to the user in accordance withinstructions received from the VR console 110. For example, hapticfeedback is provided when an action request is received or when the VRinput interface 140 receives instructions from the VR console 110causing the VR input interface 140 to generate haptic feedback when theVR console 110 performs an action.

The VR console 110 provides content to the VR headset 105 forpresentation to the user in accordance with information received fromone or more of: the imaging device 135, the VR headset 105, and the VRinput interface 140. In the example shown in FIG. 1, the VR console 110includes an application store 145, a tracking module 150, and a virtualreality (VR) engine 155. Some embodiments of the VR console 110 havedifferent modules than those described in conjunction with FIG. 1.Similarly, the functions further described below may be distributedamong modules of the VR console 110 in a different manner than describedhere.

The application store 145 stores one or more applications for executionby the VR console 110. An application is a group of instructions, thatwhen executed by a processor, generates content for presentation to theuser. Content generated by an application may be in response to inputsreceived from the user via movement of the VR headset 105 or the VRinterface device 140. Examples of applications include: gamingapplications, conferencing applications, video playback application, orother suitable applications.

The tracking module 150 calibrates the VR system environment 100 usingone or more calibration parameters and may adjust one or morecalibration parameters to reduce error in determining of the position ofthe VR headset 105 or of the VR input device 140. For example, thetracking module 150 adjusts the focus of the imaging device 135 toobtain a more accurate position for observed locators on the VR headset105. Moreover, calibration performed by the tracking module 150 alsoaccounts for information received from the IMU 130. Additionally, iftracking of the VR headset 105 is lost (e.g., the imaging device 135loses line of sight of at least a threshold number of the locators 120on the VR headset 105), the tracking module 150 re-calibrates some orall of the VR system environment 100.

The tracking module 150 tracks movements of the VR headset 105 usingslow calibration information from the imaging device 135. For example,the tracking module 150 determines positions of a reference point of theVR headset 105 using observed locators from the slow calibrationinformation and a model of the VR headset 105. The tracking module 150also determines positions of a reference point of the VR headset 105using position information from the fast calibration information.Additionally, in some embodiments, the tracking module 150 may useportions of the fast calibration information, the slow calibrationinformation, or some combination thereof, to predict a future locationof the VR headset 105. The tracking module 150 provides the estimated orpredicted future position of the VR headset 105 to the VR engine 155.

The VR engine 155 executes applications within the VR system environment100 and receives position information, acceleration information,velocity information, predicted future positions, or some combinationthereof of the VR headset 105 from the tracking module 150. Based on thereceived information, the VR engine 155 determines content to provide tothe VR headset 105 for presentation to the user. For example, if thereceived information indicates that the user has looked to the left, theVR engine 155 generates content for the VR headset 105 that mirrors theuser's movement in a virtual environment. Additionally, the VR engine155 performs an action within an application executing on the VR console110 in response to an action request received from the VR inputinterface 140 and provides feedback to the user that the action wasperformed. The provided feedback may be visual or audible feedback viathe VR headset 105 or haptic feedback via the VR input interface 140.

FIG. 2A is a diagram of a virtual reality (VR) headset, in accordancewith an embodiment. The VR headset 200 is an embodiment of the VRheadset 105, and includes a front rigid body 205 and a band 210. Thefront rigid body 205 includes an electronic display element of theelectronic display 115 (not shown in FIG. 2), the optics block 118 (notshown in FIG. 2), the IMU 130, the one or more position sensors 125, aneye tracking unit 160 (not shown in FIG. 2), and the locators 120. Inthe embodiment shown by FIG. 2, the position sensors 125 are locatedwithin the IMU 130, and neither the IMU 130 nor the position sensors 125are visible to the user.

The locators 120 are located in fixed positions on the front rigid body205 relative to one another and relative to a reference point 215. Inthe example of FIG. 2, the reference point 215 is located at the centerof the IMU 130. Each of the locators 120 emit light that is detectableby the imaging device 135. The locators 120, or portions of the locators120, are located on a front side 220A, a top side 220B, a bottom side220C, a right side 220D, and a left side 220E of the front rigid body205 in the example of FIG. 2.

FIG. 2B is a cross section 225 of the front rigid body 205 of theembodiment of a VR headset 200 shown in FIG. 2A. The FIG. 2B shows acompound display assembly 160 that includes the optics block 220, acombined display element 225. The compound display assembly 160 emitsimage light toward the optics block 220. The optics block 220 combinesthe image light, and in some embodiments, magnifies the image lightand/or corrects for one or more additional optical errors (e.g.,distortion, astigmatism, etc.). The optics block 220 directs the imagelight to an exit pupil 240 for presentation to the user. The exit pupil240 is the location of the front rigid body 205 where a user's eye 250is positioned.

Additionally, in some embodiments, the compound display includes an eyetracking unit 215. The eye tracking unit 215 tracks eye movement of theeye 250. For purposes of illustration, FIG. 2B shows a cross section 225associated with a single eye 250, accordingly, a separate optics block220 and/or combined display 225 may be used to provide altered imagelight to other eye of the user. Similarly, a separate eye tracking unit215 may be used to track eye movement of the other eye of the user.

The eye 250 includes a cornea 252, a pupil 254, a lens 256, an iris 258,a sclera 260, and a fovea 262. The fovea 262 is illustrated as a smallindent on the retina. The fovea 262 corresponds to the area of retinawhich has the highest visual acuity. The angular orientation of the eyecorresponds to a direction of the user's gaze within the VR headset 105and is defined herein as the direction of a foveal axis 264, which isthe axis between a fovea of the eye and a center of the eye's pupil 254.In general, when a user's eyes are fixed on a point, the foveal axes ofthe user's eyes intersect that point. The eye also includes a pupillaryaxis 266, which is the axis passing through the center of the pupil 254,which is perpendicular to the corneal surface 252. In some embodiments,the eye tracking unit 215 detects an orientation of the pupillary axisand estimates the foveal axis based on the detected pupillary axis.Alternately, the eye tracking unit 215 estimates the foveal axis bydirectly detecting a location of the fovea or of other features of theeye's retina.

FIG. 3 is a high-level block diagram illustrating a detailed view ofmodules within a compound display assembly 300, in accordance with anembodiment. In some embodiments, the compound display assembly 300 is acomponent (e.g., compound display assembly 160) of the VR headset 105.In alternate embodiments, the compound display assembly 300 is part ofsome other HMD, or other system that generates images at retinalresolution.

The compound display assembly 300 includes a combined display element305 that further includes at least one peripheral display 315 and onehigh resolution inset display 324, an optics block 320, a controller 327and an optional eye tracking unit 322. The combined display element 305,the optics block 320, and the eye tracking unit 322 are substantiallysimilar to the combined display element 225, the optics block 220, andthe eye tracking unit 215, respectively.

The compound display assembly 300 displays composite content to the user(e.g., in accordance with data received from a VR console 110).Composite content includes an inset region and a background region. Theinset region includes a HR inset portion of an image and a transitionalportion of the image. The HR inset portion has resolution correspondingto a resolution of a fovea region of a human eye. The transitionalportion surrounds the HR inset portion, and has a varying resolutionthat smoothly varies from resolution corresponding to the resolution ofthe fovea region to a resolution corresponding to a non-fovea region ofthe eye. The background region has a resolution corresponding to anon-fovea region of a human eye. In various embodiments, the compounddisplay assembly 300 may comprise at least two electronic displays foreach eye of a user, for example a peripheral display 315 and a highresolution (HR) inset display 324. Examples of the electronic displaysinclude: a liquid crystal display (LCD), an organic light emitting diode(OLED) display, an active-matrix organic light-emitting diode display(AMOLED), some other display, or some combination thereof.

The peripheral display 315 displays a background region of compositecontent. The peripheral display 315 receives the background region fromthe controller 327. In some embodiments, the peripheral display 315 maysupport displaying only low resolution content (e.g., it may berelatively low resolution display). In some embodiments, the peripheraldisplay 315 may support displaying content at high as well as lowresolution content.

The HR inset display 324 displays the inset region portion of thecomposite content. The HR inset display 324 has at least a resolutioncapable of displaying the HR inset portion of the image at its fullresolution. Along the periphery of the inset region the HR inset displaydisplays the transitional portion of the image with the varyingresolution. The HR inset display 324 receives the inset portion from thecontroller 327.

In some embodiments, the optical properties of the HR inset 324 andperipheral display 315 are “well matched.” For example, a virtual imagedistance of the HR inset 324 and peripheral display 315 are with athreshold distance from each other. The threshold distance is determinedby an amount of dioptric separation. The HR inset 324 and peripheraldisplay 315 are also well matched in the sense that one or moreaberrations (e.g., field curvature, astigmatism, longitudinal chromaticaberration, etc.) for both displays are within a threshold amount. Ifthe HR inset 324 and peripheral display 315 are not well matched, it mayimpede matching the virtual image distance for the HR inset 324 andperipheral display 315 when the inset is steered over the field of view.

In some embodiments, an eye tracking unit 322 is included in thecompound display assembly 300. The eye tracking unit 322 determines aneye's position, including orientation and location of the eye includingthe location of the foveal axis of the eye relative to the combineddisplay element 305. An eye tracking unit 322 may include an imagingsystem to image one or both eyes and may optionally include a lightemitter, which generates light that is directed towards an eye so lightreflected by the eye may be captured by the imaging system. For example,the eye tracking unit 322 includes a coherent light source emittinglight in the visible spectrum or infrared spectrum as well as a cameracapturing reflections of the emitted light by the user's eye. As anotherexample, the eye tracking unit 322 captures reflections of radio wavesemitted by a miniature radar unit. The eye tracking unit 322 useslow-power light emitters that emit light at frequencies and intensitiesthat do not injure the eye or cause physical discomfort. In variousother embodiments, the eye tracking unit 322 measures electromagneticenergy reflected by the eye and communicates the measuredelectromagnetic energy to the eye tracking unit 322, which determinesthe eye's position based on the measured electromagnetic energy.

In some embodiments, the compound display assembly 300 is configured togenerate composite content having a fixed inset region. A fixed insetregion is an inset region that is fixed in relation to the backgroundregion. The fixed inset region does not change its location with themovement of the eye. In some embodiments, the fixed inset region islocated in an inset area located in a center of the background region(see e.g., FIG. 9A). In other embodiments, the fixed inset region islocated at some other location (e.g., may be off-center). In theseembodiments, the optics block 320 may also include an opticalanti-aliasing filter. The optical anti-aliasing filter is an opticalelement that optically blurs the background region of the compositecontent. This helps remove digital artifacts due to the nature of thedisplay and make the blur of the background region more natural.

The optics block 320 combines the content from the peripheral display315 and the HR inset display 324 to form a composite content at retinalresolution. The optics block 320 may include a directing optical elementsuch as a beam splitter. The directing optical element combines imagelight (i.e., background region) from the peripheral display 315 andimage light (i.e., inset region) from the HR inset display 324 togenerate composite content. The optics block 320 directs the compositecontent towards an exit pupil of the compound display assembly 300.

Additionally, the optics block 320 may magnify the composite content orcorrect optical errors associated with the composite content, and thecorrected composite content is presented to a user of the VR headset105. In various embodiments, the optics block 320 includes one or moreoptical elements. Example optical elements include: a beam splitter, oneor more mirrors, one or more steerable mirrors and/or lenses, Risleyprisms, phase-only spatial light modulators, decentered lenses, anaperture, a Fresnel lens, a convex lens, a concave lens, a filter, orany other suitable optical element that affects the image light emittedfrom the combined display element 340. Moreover, the optics block 320may include combinations of different optical elements. In someembodiments, one or more of the optical elements in the optics block 320may have one or more coatings, such as partial reflectors oranti-reflective coatings.

The optics block 320 may include a steering element. A steering elementis one or more optical elements that adjusts a location (e.g. angularlyor spatially) of the inset region in the composite content. The steeringelement may be, e.g., a steerable mirror. In other embodiments, thesteering element may include Risley prisms, phase-only spatial lightmodulators, decentered lenses, or some combination thereof. The steeringelement adjusts a position of the inset region in the composite contentin accordance with steering instructions from the controller 327.

Magnification of image light by the optics block 320 allows the combineddisplay element 340 to be physically smaller, weigh less, and consumeless power than larger displays. Additionally, magnification mayincrease a field of view of displayed composite content. For example,the field of view of the displayed composite content is such that thedisplayed content is presented using almost all (e.g., 110° diagonal),and in some cases all, of the user's field of view.

The optics block 320 may be designed to correct one or more types ofoptical error. Examples of optical error include: two dimensionaloptical errors, three dimensional optical errors, or some combinationthereof. Two dimensional errors are optical aberrations that occur intwo dimensions. Example types of two dimensional errors include: barreldistortion, pincushion distortion, longitudinal chromatic aberration,transverse chromatic aberration, or any other type of two-dimensionaloptical error. Three dimensional errors are optical errors that occur inthree dimensions. Example types of three dimensional errors includespherical aberration, chromatic aberration, field curvature,astigmatism, or any other type of three-dimensional optical error. Insome embodiments, content provided to the combined display element 340for display is pre-distorted, and the optics block 320 corrects thedistortion when it receives image light from the combined displayelement 340 generated based on the content.

The controller 327 divides an image (or series of images) into an HRinset portion, a transitional portion, and a peripheral portion. In someembodiments, the controller 327 adjusts the resolution (e.g., upsampleor downsample) of the HR inset portion such that it corresponds to atarget resolution of an inset region. The target resolution is aresolution corresponding to a fovea region of a human eye. In someembodiments, the target resolution may be a resolution of the HR insetdisplay 324. In some embodiments, the resolution of the HR inset portionis at the resolution of the HR inset display 324 so no adjustment isneeded. The resulting content corresponds to the inset region of thecomposite content. Likewise, in some embodiments, the controller 327adjusts (e.g., downsamples) the resolution of the peripheral portionsuch that it corresponds to the resolution of a background region of thecomposite content (e.g., may be a resolution of the peripheral display315). The resulting content corresponds to the background region of thecomposite content.

The controller 327 applies a blending function to adjust the resolutionof transitional portion such that the resolution smoothly transitionsfrom a resolution of the HR inset portion of the image to the resolutionof the background region. The blending function corresponds to the falloff in acuity associated with a transition from a fovea to a non-fovearegion of a human eye. The blending function may be, for example, aGaussian pyramid decomposition function, a Gaussian blending function,some function that smoothly transitions from the resolution of the insetregion to the resolution of the background region, or some combinationthereof. Additionally, the pyramid blending function may includeperforming a Gaussian pyramid decomposition, i.e., smoothen the contentwith an appropriate smoothing filter and then subsample the smoothedcontent and continue the process for a predetermined level of samplingdensity. The sub sampled and smoothened content is blended to theoriginal content using a Gaussian blending function. The blendedtransitional portion corresponds to the transitional region of thecomposite content.

The controller 327 may also fade (e.g. the light is reduced in thesection of the resulting image) the peripheral portion and/or thetransitional portion using an intensity fading function. The content mayinclude regions that have variable amounts of fading. Each region istermed as a fading region. The boundary of a fading region is determinedusing a size of the inset region. In some embodiments, the intensityfading function is applied to the image that causes an inset area in thebackground region to fade to black. And similarly, a different intensityfading function may be applied to some of the transitional portion ofthe image that surrounds the HR inset portion of the image.

The controller 327 provides, for display, the inset region to the HRinset display 324. The controller 327 also provides, for display, thebackground region to the peripheral display 315.

In some embodiments, the controller 327 receives information related tomovement of the eye from an eye tracking unit 322. Based on theinformation related to the movement of the eye, the controller 327determines a gaze direction of a user and a corresponding location of afovea region of the eye of the user. The gaze direction corresponds tothe foveal axis discussed above with regard to FIG. 2B. The controller327 generates steering instructions for a steering element to adjust aposition of the inset region such that it stays centered on thedetermined gaze direction. In such embodiments, the controller 327 alsodynamically generates and/or adjusts the inset region and/or thebackground region to account for the moving location of the insetregion.

In some embodiments, an output of a graphics card of the compounddisplay assembly 300 renders with spatially varying resolution based inpart on the determined gaze direction. For example the rendered contentwould include a HR portion corresponding to the gaze location, and aperipheral-low resolution portion. In some embodiments, theperipheral-low resolution portion includes a transitional area thatblends the low resolution content with the high resolution content. Inalternate embodiments, the HR portion is enclosed by the transitionalarea. The controller 327 then separates the rendered content into the HRportion for the HR inset display 324 and the peripheral-low resolutionportion for the peripheral display 315, and provides the HR portion tothe HR inset display 324 and the peripheral-low resolution portion tothe peripheral display 315. In this manner, rendering at full resolutionand downsampling is avoided, which would be unnecessary and potentiallycomputationally wasteful.

In the above embodiments, the transitional region is part of the insetregion. In alternate embodiments, the compound display assembly 300 ismodified such that the transitional portion of the image is part of thebackground region. In these embodiments, the inset region is composed ofthe HR inset portion of the image, and the background region is composedof the downsampled peripheral region that surrounds a blendedtransitional region. In such embodiments, the peripheral display 315 iscapable of displaying images at a resolution of at least that of the HRinset portion.

FIG. 4A are example non-pupil forming designs 400 of a compound displayassembly configured to generate composite content having a fixed insetregion, in accordance with an embodiment. The non-pupil forming design400 includes a design 402 having a 45 degree beam splitter and a design404 with a canted beam splitter. The design 402 includes a peripheraldisplay 406, a HR inset display 408, a beam splitter 410, and an opticalelement 412 (e.g., a positive lens).

The peripheral display 406 emits light corresponding to a backgroundregion (and possibly some or all of a transitional region) of compositecontent. The HR inset display 408 emits light corresponding to an insetregion of the composite content. The light from the peripheral display406 and the HR inset display 408 is combined using a directing optic(i.e., the beam splitter 410) to generate a composite image thatincludes an inset region and a background region.

The design 404 is substantially similar to the design 402, except thebeam splitter 410 is canted such that its normal is not 45 degrees fromthe light received from the peripheral display 406 and the lightreceived from the HR inset display 408 By having an angle different than45 degrees, the system may be smaller (smaller form factor) and lighterfor the user.

FIG. 4B are example pupil forming designs 420 of a compound displayassembly configured to generate composite content having a fixed insetregion, in accordance with an embodiment. The pupil forming designs 420include a unit-magnification design 425 and a de-magnified design 427.

The unit magnification design 425 includes a peripheral display 430, aHR inset display 435, a beam splitter 440, peripheral imaging lens 445,inset imaging lens 450, and an output lens 455. The emitted light fromthe peripheral display 430 is focused to an intermediate image point 460by the peripheral lens 445 and the beam splitter 440. The emitted lightfrom the HR inset display 435 is focused to the intermediate image point460 by the inset imaging lens 450 and the beam splitter 440. In thedesign 425 the intermediate image is composite content, and is a unitmagnification of a combination of the light emitted from the peripheraldisplay 430 and the HR inset display 435. The output lens 455 outputsthe composite content toward, e.g., an exit pupil of the design 425.

The design 427 is substantially similar to the design 425, except the HRinset display 435 is replaced with a large inset display 465, and theinset lens 450 is configured to de-magnify the light from the largeinset region display 465 that is focused on the intermediate image point460. The large inset display 465 may have a resolution lower than the HRinset display 435. The de-magnification of the large inset display 465results in an apparent increase in resolution at the intermediate imagepoint 460. In fact, composite content located at the intermediate imagepoints 460 for both designs 425 may have equal resolution—even thoughthe large inset display 465 has a lower resolution than the HR insetdisplay 435.

One advantage of pupil forming designs 400 is that the generation of anintermediate image provides a longer path length from the peripheral andinset region displays to the exit pupil of a user. This allows insertionof optical elements to display a high quality composite image at theexit pupil. The additional number of lenses may provide for opticalcorrection as well.

The size of the inset region in the composite content is determinedbased on high level design rules that are determined based on the visualacuity of an eye. The acuity chart of a human eye and a variety ofdisplays are explained in detail below with respect to FIG. 5.

FIG. 5 illustrates acuity for a human eye and various displays, inaccordance with an embodiment. The acuity chart of FIG. 5 plotseccentricity 505 (i.e. field of view, of a human eye or a virtualdisplay device) versus the resolution 510 of the content. The plot 515is for visual acuity of a human eye. The resolution of content is at itspeak at 0 degrees of eccentricity. This is the ideal field of view of ahuman eye, i.e. the visibility of content is the sharpest at this point.As the field of view moves away from the center by a few degrees, theresolution starts decreasing by a fair amount, i.e. the visibility ofcontent is less sharp in this region (i.e. +/−20 degree eccentricity).As the field of view further moves away, i.e. around +/−40 degrees,+/−60 degrees, etc., the resolution drops sharply, i.e. the visibilityof content starts fading out. The area around +/−20 degrees eccentricityfor a visual acuity 505 curve is typically the fovea region of the humaneye.

The plot 520 is for a display A, for example, an OLED based microdisplaydevice. The plot 520 is the closest to the visual acuity, i.e. produceshigh resolution content in the range of +20 to −20 degrees eccentricity.Based on the plot 520, the display A provides HR content (e.g. 38 cyclesper degree) at a +/−10 degrees of eccentricity.

The plot 525 is for a display B. Based on the plot 525, the resolutionof the content is low compared to other displays, for example, displayA, display C, display D in the acuity chart. For example, the resolutionof the plot 525 is 8 cycles per degree resolution, at 0 degrees ofeccentricity. For a wide range of eccentricity +/−30 degrees, theresolution remains at around 8 cycles per degree. Based on this plot525, the display B provides low resolution content.

A region 530 shows a zoomed in version of an intersection 535 of highresolution plot 540, plot 545, plot 520 and low resolution plot 525.From the zoomed in region 530, a resolution of the inset region designis designed to be in the region around the intersection 535 of the highresolution plot 520 and low resolution plot 525. The high resolutionportion of the HR inset display is designed to be at least as high as orhigher than the peak visual acuity point 550. Additionally, theperipheral portion, i.e. the low resolution portion in the background issupported by a peripheral display that has a resolution similar to theplot 525. A combined display with varying resolution exceeds humanvisual system as a function of eccentricity.

FIG. 6A is an example design 600 of a compound display assembly 602configured to generate composite content having a fixed inset region, inaccordance with an embodiment. The compound display assembly 602 is anembodiment of the compound display assembly 300 discussed above.

The design 600 includes a peripheral display 610, a HR inset display605, and a ball structure 615, and an output lens 620. The peripheraldisplay 610 is an embodiment of the peripheral display 315, and the HRinset display 605 is an embodiment of the HR inset display 324.

The ball structure 615 and the output lens 620 make up an optics block(e.g., the optics block 320). The ball structure 615 is a high indexmaterial (e.g., an acrylic) that includes a beam splitting interface625. A high index material is a material with an index of refractiongreater than 2. The peripheral display 610 is coupled to a curvedsurface of the ball structure 615. Similarly, the HR inset display 605is coupled to a different curved surface of the ball structure 615.

In some embodiments, the peripheral display 610 and the HR inset regiondisplay 605 are curved displays. A curved display may mitigate fieldcurvature, which is a form of optical distortion. In some embodiments,one or both of the peripheral display 610 and the HR inset display 605are flat displays that are coupled to the curved surfaces of the ballstructure 615 using respective fiber tapers.

Light from the peripheral display 610 and the HR inset display 605 arecombined in the ball structure 615 to form composite content. Thecomposite content is directed toward the output lens 620, which thendirects the composite content towards an exit pupil 240. The light maypass through a baffling system before reaching the exit pupil.

FIG. 6B is a perspective view of a compound display assembly 602, inaccordance with an embodiment. The compound display assembly 602 is anembodiment of the compound display assembly 300 discussed above. Thecompound display assembly 602 is configured to present compositecontent. The compound display assembly 602 illustrates axes 630,peripheral displays 610, and HR inset displays 605. The axes 630 areconfigured to align within a fovea region of eyes of a user whose gazelocation is at the center of the composite content—accordingly, thecompound display assembly 602 is configured to provide a fixed insetregion.

FIG. 6C is a top view of the compound display assembly 602 shown in FIG.6B, in accordance with an embodiment. The compound display assembly 602illustrates the axes 630, the peripheral displays 610, the HR insetdisplays 605, and the ball structures 615.

FIG. 7 is an example design of a compound display assembly 700configured to generate composite content including a steered highresolution inset, in accordance with some embodiments. The compounddisplay assembly 700 is an embodiment of the compound display assembly300 discussed above.

The compound display assembly 700 includes an inset region display 705,a group 710 of optical elements, a steering element 715, a group 720 ofoptical elements, a peripheral display 725 and a beam splitter 730.

The inset region display 705 emits light toward the group 710 of opticalelements. The light is an inset portion of the composite content, and insome embodiments may include some or all of the transitional region ofthe composite content.

The group 710 of optical elements directs light from the inset regiondisplay 705 to the steering element 715. The group 710 includes aplurality of positive and negative lenses. The group of optical elementshelps collimate the light to reduce the impact of the steering elementchanges as the beam moves around.

The steering element 715 moves the inset region portion in accordancewith steering instructions from a controller (e.g., the controller 320).The steering instructions generally keep the inset region portion ofcomposite content centered on a user's gaze location (i.e., aligned witha fovea region of an eye of the user). Examples of steering elementsinclude a steering mirror, prisms, lenses, light modulators and othersuch elements. The steering element 715 has a large clear aperture, afast response time (e.g. less than 10 milliseconds) and a fast settlingtime (e.g. less than 1 millisecond) and an accurate angular deviation(e.g. less than at least one pixel angular dimension over the emittedlight duty-cycle to avoid perceiving the motion of the representedimage). The response time is the time the steering element 715 takes torespond to a received change of movement. The settling time is theamount of time the steering element 715 takes to adjust to the newlocation after responding to the change of movement. A fast responsetime and fast settling time allow the steering element to move the insetregion movement at the speed of the eye movement or faster. Similarlythe accurate angular deviation is important to align the inset regionportion at the location of the fovea region of the eye with the improvedresolution limits.

The group 720 of optical elements direct the steered light toward thebeam splitter 730. The peripheral display 725 emits light toward thebeam splitter 730. The emitted light is the background region of thecomposite content and may include some or all of the transitional regionof the composite content.

The beam splitter 730 combines the light from the group of optics 720with the light from the peripheral display 725 to generate compositecontent. The output lens 735 then directs the composite content to anexit pupil 740. In one embodiment, the light may be directed through abaffling system.

FIG. 8 is flowchart for generating an image at retinal resolution, inaccordance with some embodiments. The process 800 may be performed bythe compound display assembly 800 in some embodiments. The compounddisplay assembly 800 is an embodiment of the compound display assembly300. Alternatively, other components may perform some or all of thesteps of the process 800. For example, in some embodiments, a HMD and/ora VR console may perform some of the steps of the process 800.Additionally, the process 800 may include different or additional stepsthan those described in conjunction with FIG. 8 in some embodiments orperform steps in different orders than the order described inconjunction with FIG. 8.

The compound display assembly 800 divides 810 an image into a HR insetportion, a peripheral portion, and a transitional portion. Thetransitional portion is a portion of the image between the HR insetportion and the peripheral portion. In some embodiments, the image is ata first resolution that corresponds to a fovea region of a human eye. Inother embodiments, the compound display assembly 800 adjusts (e.g.,downsamples or upsamples) a resolution of the image to match the firstresolution.

In embodiments, as part of the division, an intensity fading function isapplied to the image that causes the inset portion and the transitionalportion to fade to black, but not fade the peripheral portion of theimage (see, e.g., FIG. 9A). And similarly, a different intensity fadingfunction may be applied to some of the transitional portion of the imagethat surrounds the HR inset (see, e.g., FIG. 9B).

The compound display assembly 800 downsamples 820 the peripheral portionto a second resolution that is less than the first resolution. Thesecond resolution corresponding to a non-fovea region of the human eye.

The compound display assembly 800 blends 830 the transitional portion ofthe image. The transitional portion has an inner boundary between thetransitional portion and the HR inset portion and an outer boundarybetween the transitional portion and the peripheral portion. Theblending is such that there is a smooth change in resolution from theinner boundary at the first resolution to the outer boundary at thesecond resolution. The smooth change corresponds to a change inresolution between the fovea region and the non-fovea region. Theblending may be done using, e.g., a blending function. The blendingfunction may, e.g., smooth the content with an appropriate smoothingfilter and then subsample the smoothed content and continue the processfor a predetermined level of sampling density. The content displayassembly 800 then blends the sub sampled and smoothened content with theoriginal content (e.g., using a Gaussian blending function).

The compound display assembly 800 generates 840 an inset region usingthe HR inset portion of the image and the blended transitional portionof the image. The inset region has a particular inset size that matchesthe outer boundary of the transitional portion of the image.

The compound display assembly 800 generates 850 a background regionusing the downsampled peripheral portion. The background region isgenerally the downsampled peripheral portion of the image. Thebackground region includes an inset area that is the inset size. Note,in embodiments, where the compound display assembly 800 is configured toprovide a steered inset, the location of the inset area in thebackground region varies to match a gaze direction of a user of the HMD.The gaze direction is determined based on a detected eye orientationfrom an eye tracking unit.

The compound display assembly 800 displays 860 the inset region using aHR inset display on a head-mounted display (HMD).

The compound display assembly 800 displays 870 the background regionusing a peripheral display on the HMD.

The compound display assembly 300 combines 880 the displayed insetregion with the displayed background region to generate compositecontent. The combination of the inset region and the background regionis done using an optics block. The inset region is inset into the insetarea of the background region. The composite image is at retinalresolution. The composite content includes low resolution content (i.e.,the background region) and high resolution content (i.e., the insetregion) displayed in an inset of the low resolution content.

Note, in embodiments where the compound display assembly 800 isconfigured to operate as a fixed inset, the compound display assembly300 may include an optical anti-aliasing filter that optically blurssome of the background region. This helps remove digital artifacts orblockiness and make the blur of the background region more natural.

Additionally, in some embodiments, the compound display assembly 800calibrates color for the peripheral display and the inset display suchthat they both are within a threshold range of color values. As theperipheral display and the inset display are two separate displays, thecolor calibration matches color across the two sensors such that anycolor shift between the sensors is not detectable to a viewing user. Inone embodiment, the color calibration may occur dynamically to accountfor variation in the beam splitter performance.

In some embodiments, the compound display calibrates luminance for theperipheral display and the inset display such that they both are withina threshold range of luminance values. Similar to color calibration, theluminance calibration matches luminance across the two sensors such thatany luminance shift between the sensors is not detectable to a viewinguser.

FIG. 9A illustrates a background region 900 of an image displayed via aperipheral display, in accordance with some embodiments. The backgroundregion 900 illustrates a low resolution portion 910 and an inset area920. The low resolution portion 910 is at a low resolution generallycorresponding to a resolution of a non-fovea region of a human eye. Theinset area 920 is location where the inset region may be combined withthe background region 900 to generate composite content.

FIG. 9B illustrates an inset region 930 of an image displayed via a HRinset display, in accordance with some embodiments. The inset region 930includes a HR inset portion 940 of the image and a transitional portion950 of the image. The HR inset portion 940 is at a resolutioncorresponding to a foveal region of a human eye. The HR inset portion940 is surrounded by the transitional portion 950. The transitionalportion 950 has an outer boundary 955 and an inner boundary 960. Thetransitional portion 950 is blended such that the resolution smoothlyvaries from the outer boundary 955 at the resolution of the lowresolution portion 910 discussed above, to the high resolution of the HRinset portion 940. Additionally, the transitional portion 950 may befaded to ensure that it combines correctly with the background region900.

FIG. 9C illustrates composite image 970 including variable resolutionsdisplayed via a compound display assembly, in accordance with someembodiments. The composite image 970 includes the inset region 930 andthe background region 900.

Additional Configuration Information

The foregoing description of the embodiments of the disclosure have beenpresented for the purpose of illustration; it is not intended to beexhaustive or to limit the disclosure to the precise forms disclosed.Persons skilled in the relevant art can appreciate that manymodifications and variations are possible in light of the abovedisclosure.

Some portions of this description describe the embodiments of thedisclosure in terms of algorithms and symbolic representations ofoperations on information. These algorithmic descriptions andrepresentations are commonly used by those skilled in the dataprocessing arts to convey the substance of their work effectively toothers skilled in the art. These operations, while describedfunctionally, computationally, or logically, are understood to beimplemented by computer programs or equivalent electrical circuits,microcode, or the like. Furthermore, it has also proven convenient attimes, to refer to these arrangements of operations as modules, withoutloss of generality. The described operations and their associatedmodules may be embodied in software, firmware, hardware, or anycombinations thereof.

Any of the steps, operations, or processes described herein may beperformed or implemented with one or more hardware or software modules,alone or in combination with other devices. In one embodiment, asoftware module is implemented with a computer program productcomprising a computer-readable medium containing computer program code,which can be executed by a computer processor for performing any or allof the steps, operations, or processes described.

Embodiments of the disclosure may also relate to an apparatus forperforming the operations herein. This apparatus may be speciallyconstructed for the required purposes, and/or it may comprise ageneral-purpose computing device selectively activated or reconfiguredby a computer program stored in the computer. Such a computer programmay be stored in a non-transitory, tangible computer readable storagemedium, or any type of media suitable for storing electronicinstructions, which may be coupled to a computer system bus.Furthermore, any computing systems referred to in the specification mayinclude a single processor or may be architectures employing multipleprocessor designs for increased computing capability.

Embodiments of the disclosure may also relate to a product that isproduced by a computing process described herein. Such a product maycomprise information resulting from a computing process, where theinformation is stored on a non-transitory, tangible computer readablestorage medium and may include any embodiment of a computer programproduct or other data combination described herein.

Finally, the language used in the specification has been principallyselected for readability and instructional purposes, and it may not havebeen selected to delineate or circumscribe the inventive subject matter.It is therefore intended that the scope of the disclosure be limited notby this detailed description, but rather by any claims that issue on anapplication based hereon. Accordingly, the disclosure of the embodimentsis intended to be illustrative, but not limiting, of the scope of thedisclosure, which is set forth in the following claims.

What is claimed is:
 1. A head-mounted display (HMD) comprising: a highresolution (HR) inset display that is configured to display an insetregion, the inset region comprising a high resolution (HR) inset portionof an image and a transitional portion of the image, the HR insetportion at a first resolution, and the transitional portion is blendedsuch that there is a smooth change in resolution from the firstresolution to a second resolution that is lower than the firstresolution; a peripheral display that is configured to display abackground region, the background region having a second resolution thatis less than the first resolution, the second resolution correspondingto a resolution of a non-fovea region of the human eye; an eye trackingunit that is configured to detect movement of an eye of a user of theHMD; an optics block configured to: combine the inset region and thebackground region to create composite content, wherein the inset regionis inset into the background region, and direct the composite content toan exit pupil of the HMD corresponding to a location of the eye; and acontroller configured to: receive, from the eye tracking unit,information related to movement of the eye, determine, based on theinformation, a gaze direction of the user representing an axis between afovea of the eye of the user and a center of a pupil of the eye, andsend steering instructions to a steering element of the optical block toadjust a position of the inset region relative to the background regionsuch that the inset region is centered on the determined gaze direction.2. The HMD of claim 1, further comprising: an optical anti-aliasingfilter that optically blurs a portion of the background content.
 3. TheHMD of claim 1, wherein the composite content has variable resolutionthat matches a resolution of a retina of a human eye.
 4. The HMD ofclaim 1, wherein the controller is further configured to generate thebackground region and the inset region.
 5. The HMD of claim 1, whereinthe optics block includes the steering element that, responsive toinstructions received from the controller, is configured to adjust aposition of the inset region in the composite content.
 6. The HMD ofclaim 1, wherein the optics block includes a beam splitter that combinesthe inset region and the background region to create the compositecontent.
 7. The HMD of claim 6, wherein the beam splitter is within aball structure.
 8. The HMD of claim 7, wherein the peripheral display isa curved display that is coupled directly to a curved surface of theball structure.
 9. The HMD of claim 7, further comprising a fiber taperhaving a first surface and a second surface, and the peripheral displayis a flat display that is coupled to the first surface of the fibertaper, and the second surface of the fiber taper is curved and iscoupled to a curved surface of the ball structure.
 10. The HMD of claim1, wherein the first resolution corresponds to a resolution of a fovearegion of a human eye.
 11. The HMD of claim 1, wherein the firstresolution is lower than a corresponding resolution of a fovea region ofa human eye, and the HR inset display is a large inset display, and theoptics block is configured to de-magnify the inset region displayed bythe large inset display to increase its resolution.
 12. A head-mounteddisplay (HMD) comprising: a high resolution (HR) inset display that isconfigured to display an inset region, the inset region comprising ahigh resolution (HR) inset portion of an image and a transitionalportion of the image, the HR inset portion of the image at a firstresolution, and the transitional portion is blended such that there is asmooth change in resolution from the first resolution to a secondresolution that is lower than the first resolution; a peripheral displaythat is configured to display a background region, the background regionhaving a second resolution that is less than the first resolution, thesecond resolution corresponding to a resolution of a non-fovea region ofthe human eye; an eye tracking unit that is configured to detectmovement of an eye of a user of the HMD; an optics block including: abeam splitter that combines the inset region displayed by the HR insetdisplay and the background region displayed by the peripheral display tocreate composite content, wherein the inset region is inset into thebackground region, and an output lens that directs the composite contentto an exit pupil of the HMD corresponding to a location of the eye; anda controller that is configured to: receive, from the eye tracking unit,information related to movement of the eye, determine, based on theinformation, a gaze direction of the user representing an axis between afovea of the eye of the user and a center of a pupil of the eye, andsend steering instructions to a steering element of the optical block toadjust a position of the inset region relative to the background regionsuch that the inset region is centered on the determined gaze direction.13. The HMD of claim 12, further comprising: an optical anti-aliasingfilter that optically blurs a portion of the background content.
 14. TheHMD of claim 12, wherein the composite content has variable resolutionthat matches a resolution of a retina of a human eye.
 15. The HMD ofclaim 12, wherein the controller is further configured to generate thebackground region and the inset region.
 16. The HMD of claim 12, whereinthe optics block includes the steering element that, responsive toinstructions received from the controller, is configured to adjust aposition of the inset region in the composite content.
 17. The HMD ofclaim 12, wherein the first resolution corresponds to a resolution of afovea region of a human eye.
 18. A head-mounted display (HMD)comprising: a high resolution (HR) inset display that is configured todisplay an inset region, the inset region comprising a high resolution(HR) inset portion of an image and a transitional portion of the image,the HR inset portion of the image at a first resolution corresponding toa resolution of a fovea region of a human eye, and the transitionalportion is blended such that there is a smooth change in resolution fromthe first resolution to a second resolution that is lower than the firstresolution; a peripheral display that is configured to display abackground region, the background region having a second resolution thatis less than the first resolution, the second resolution correspondingto a resolution of a non-fovea region of the human eye; an eye trackingunit that is configured to detect movement of an eye of a user of theHMD; an optics block including: a beam splitter that combines the insetregion displayed by the HR inset display and the background regiondisplayed by the peripheral display to create composite content, whereinthe inset region is inset into the background region, and an output lensthat directs the composite content to an exit pupil of the HMDcorresponding to a location of the eye; and a controller configured to:receive, from the eye tracking unit, information related to movement ofthe eye, determine, based on the information, a gaze direction of theuser representing an axis between a fovea of the eye of the user and acenter of a pupil of the eye, and send steering instructions to asteering element of the optical block to adjust a position of the insetregion relative to the background region such that the inset region iscentered on the determined gaze direction.
 19. A head-mounted display(HMD) comprising: a high resolution (HR) inset display that isconfigured to display an inset region, the inset region comprising ahigh resolution (HR) inset portion of an image and a transitionalportion of the image, the HR inset portion at a first resolution, andthe transitional portion is blended such that there is a smooth changein resolution from the first resolution to a second resolution that islower than the first resolution; a peripheral display that is configuredto display a background region, the background region having a secondresolution that is less than the first resolution; an eye tracking unitthat is configured to detect movement of an eye of a user of the HMD; anoptics block configured to: combine the inset region and the backgroundregion to create composite content, wherein the inset region is insetinto the background region, and direct the composite content to an exitpupil of the HMD corresponding to a location of the eye; and acontroller configured to: receive, from the eye tracking unit,information related to movement of the eye, determine, based on theinformation, a gaze direction of the user representing an axis between afovea of the eye of the user and a center of a pupil of the eye, andsend steering instructions to a steering element of the optical block toadjust a position of the inset region relative to the background regionsuch that the inset region is centered on the determined gaze direction.20. The HMD of claim 19, further comprising: an optical anti-aliasingfilter that optically blurs a portion of the background content.
 21. TheHMD of claim 19, wherein the optics block includes the steering elementthat, responsive to instructions received from the controller, isconfigured to adjust a position of the inset region in the compositecontent.